Partially floating marine platform for offshore wind-power, bridges and marine buildings, and construction method

ABSTRACT

A partially floating supported marine platform for offshore wind turbines, bridges and offshore buildings includes horizontal beams and hollow, cylindrically-shaped and vertically disposed buoyancy tubes interconnected to form the marine platform. A cone matching technique may be employed to fast fix the buoyancy tubes onto concrete beds in the seabed that are prepared in advance. Piling support to enhance the foundation of the platform may be used, to be installed within the buoyancy tube interior using small diameter piles that are driven down into the concrete beds and socketed into bedrock. The buoyancy tubes are capped at top and bottom ends, providing buoyancy to the platform at temporary and/or at permanent states. All manual operations for installing piling support are performed in dry conditions, thus expensive piling vessels are not required, thereby providing an economical and safe technology for the development of the ocean.

BACKGROUND

1. Field

The example embodiments in general relate to a partially floating,supported offshore marine platform for supporting offshore windturbines, bridges and marine buildings, construction methods forinstalling the marine platform in a marine environment, and a method ofassembling the platform at a harbor site.

2. Related Art

Foundation types for offshore marine platforms may be classified intothree groups: the gravity type, pile supported type, and the floatingtype covering water depths from shallow, medium to deep, respectively.For wind turbine and bridge structures, the horizontal forces due towind, waves, surges and earthquakes are likely to be the controllingload cases, since the structural dead weight is small. However, this maynot be the case for building structures on the offshore marine platform,as the gravity load is relatively large.

In the case where horizontal forces control the design, the use oftension piles is more effective than using ballast for the increase ofdead weight of the foundation, except that the bearing stratum for thefoundation is strong, i.e., bedrock, so the bearing stratum may sustainthe weight of the ballasted structures. On the other hand, in the casewhere vertical forces control the design of the marine platform, the useof a gravity type foundation is effective if the founding layer is closeto the surface of the seafloor (i.e., shallow depths), such thatexcavation of soft materials in the seafloor will not be in asubstantial quantity. The gravity type will be advantageous; but toreduce the strength demand for the founding layer, it is desirable toeither increase the contact area of the platform or reduce the loadsthereon. In the case of a piled foundation, the challenges areperforming piling operations at sea, as well as the construction of apile cap for the platform in the water.

SUMMARY

An example embodiment is directed to a partially floating, supportedoffshore marine platform for offshore wind turbines, bridges and marinebuildings, the platform adapted for a water depth greater than 5 metersin a marine environment. The platform includes at least one hollow,cylindrical buoyancy tube having a tapered lower end and disposedvertically in the marine environment. The tapered lower end may beembodied as a conically-shaped bottom slab with the apex of thecone-shaped bottom slab pointing downward towards a seabed. Thecone-shaped bottom slab of the at least one buoyancy tube is fixed to aconcrete bed that has been cast on the seabed so as to support one of awind turbine, bridge, and marine building on the marine platform in themarine environment.

Another example embodiment is directed to a method of assembling amarine platform at a harbor site, the platform to be used for supportingoffshore wind turbines, bridges and marine buildings in a marineenvironment. The method includes segmental match casting, in a factoryor casting yard, of a plurality of first segments to be assembled into ahollow, cylindrical buoyancy tube to be disposed vertically in themarine environment, the assembled marine platform to include a pluralityof buoyancy tubes, and segmental match casting, in the factory orcasting yard, of a plurality of second segments to be assembled into anelongate horizontal beam to connected between adjacent buoyancy tubes,the assembled marine platform to include a plurality of horizontalbeams. At the harbor site, at least three guiding piles are installedfor each buoyancy tube at the location of where the buoyancy tube is tobe assembled, to be used as a confining mechanism for confining a firstsegment into position and supporting the weight thereof by an overheadframe/truss.

The method further includes transporting the plurality of first segmentsto the harbor site, lifting, by use of a floating crane, a first segmentthat is to be the bottom segment of the to-be-assembled buoyancy tubeinto position, guided by the guiding piles, the bottom first segmentbeing floatable under its own weight and the weight of an immediatefirst segment placed on top of it, lifting a next first segment onto thebottom first segment and using pre-stressing to join this next firstsegment to the bottom first segment, and repeating the processes oflifting and joining for subsequent first segments to complete theassembling of the buoyancy tube, each of the assembled buoyancy tubesincluding one or more joints for connection to one or more horizontalbeams. A completed buoyancy tube is then hung so that it extendsvertically from the overhead frame/truss and is restrained by theguiding piles.

The method further includes transporting the plurality of secondsegments to the harbor site, assembling the second segments by the useof pre-stressing to join the second segments together so as to form thehorizontal beam, and lifting, by use of a floating crane, each formedhorizontal beam onto a temporary support on the guiding piles. Next,steel bars in the buoyancy tubes and horizontal beams are fixed togetherand thereafter lapping with steel. Joints where ends of horizontal beamsmeet a buoyancy tube are cast with in-situ concrete until all beams arefixed to the buoyancy tubes, completing assembly of the marine platform.The overhead frame/truss and guiding piles are removed, with theassembled marine platform configured to be floated out into the marineenvironment. Optionally, a wind turbine may be installed on top of oneof the buoyancy tubes of the platform.

BRIEF DESCRIPTION OF THE DRAWINGS

The example embodiments will become more fully understood from thedetailed description given herein below and the accompanying drawings,wherein like elements are represented by like reference numerals, whichare given by way of illustration only and thus are not limitative of theexample embodiments herein.

FIG. 1 is a perspective view of a marine platform in a marineenvironment supporting a wind turbine thereon, according to an exampleembodiment.

FIG. 2A is a front view of an example floater of the marine platform.

FIG. 2B is a bottom view of the cone-shaped bottom slab of floater 1.

FIG. 2C is an enlarged, front view of a lower section of floater 1.

FIG. 3 is a bottom view of the marine platform in another configuration,according to an example embodiment.

FIG. 4 is a side view of a marine platform with piling support in amarine environment, according to another example embodiment.

FIG. 5 is a side view to illustrate dredger operations in the marineenvironment to describe a step of excavating a seabed.

FIG. 6 is a side view to illustrate a step of concrete bed formingoperations in the seabed of the marine environment.

FIG. 7A is a side view of a single-floater platform to illustrate a stepof hovering platform just above the concrete bed.

FIG. 7B is a side view illustrating a step of lowering of thesingle-floater platform into the concrete bed 9 to form a mirror-imagereversed cone indentation in the concrete bed with the cone-shapedbottom slab.

FIG. 8A is a side view of the single-floater platform to illustrate astep of raising the platform to reveal the mirror-image reversed coneindentation in the concrete bed.

FIG. 8B is a side view of the single-floater platform to illustrate astep of again lowering the platform to rest the cone-shaped bottom slabin the mirror-image reversed cone-shaped indentation.

FIG. 9 is a side view of a marine platform fixed to a concrete bed 9 toillustrate a step of installing a small diameter pile with a boringplant.

FIG. 10A shows a boring plant executing boring of a pile using a casingfrom the top end of a marine platform.

FIG. 10B shows a piling plant driving a pile downward through a casingfrom the top of a marine platform.

FIG. 11 is a side view of a platform fixed to a concrete bed with acomplete piling support arrangement.

FIG. 12 is a perspective view which shows installation of a bridge piersupported on a marine platform, according to another example embodiment.

FIG. 13 is a perspective view of a grid formation of a marine platformemploying a plurality of interconnected floaters.

FIG. 14 is a top view illustrating a multi-platform concept comprising anumber of interconnected modules.

FIG. 16 is a side perspective view of a single-floater marine platformin which the bottom slab has a different shape configuration on anunderside thereof.

PARTS LIST

-   -   1. Floater/buoyancy tube    -   2. cone-shaped bottom slab    -   3. Regulating tower section    -   4. Stiffened ring slab    -   5. Wind turbine    -   6. Seabed/seafloor    -   7. Rubble wall/mount    -   8. Sea surface    -   9. Concrete bed    -   10. Partially floating supported offshore marine platform    -   11. Mirror-image, reversed cone-shaped indentation    -   12. Cement grout or simply grout    -   13. Soil/sand strata    -   14. Founding stratum/founding layer    -   15. Pothole    -   16. Top slab    -   17. Pile cap    -   21. Bridge pier    -   22. Dredging arm    -   23. Dredger    -   24. Boring plant/machine    -   25. Casing    -   26. Operation vessel    -   27. Small diameter piles    -   28. Piling plant/machine    -   31. Tremie concrete pipe    -   35. Bridge column    -   36. Capping beam    -   37. Pressure pipe    -   38. Valve    -   39. Recess hole    -   40. Bedrock    -   41. Embedded bar connectors    -   42. Pile cap reinforcement bars    -   43. Exposed steel bars in piling    -   45. Raking pile    -   46. Multiple cone shapes    -   47. Mirror-image, reversed, multi-cone-shaped indentations    -   48. Short steel bars

DETAILED DESCRIPTION

As will be described in further detail hereafter, example embodiments ofthe present application address the challenges discussed above in thebackground section, by describing the employment of a cone matchingtechnique to assist in attaching a hollow cylindrical buoyancy tubevertically arranged in a marine environment, also referred to as a“floater” hereafter, to a concrete bed that is formed in the seafloor,so as to compensate part of the gravity load at temporary and/orpermanent states. Additionally, the example marine platform andconstruction methods therefor may include a piling support arrangementcomprising a plurality of pilings that are inserted through the insideof the hollow floater and down into the marine environment to connectthe floater to bedrock, thereby accomplishing piling installment taskswithout requiring an expensive piling vessel at sea.

Innovative techniques exemplified by the example embodiments may furtherinclude replacing the usual solid vertical pier or column used in aconventional offshore platform with the hollow, cylindrical, verticallyarranged buoyancy tube (floater) which provides buoyancy, so that asingle floater or a plurality of interconnected floaters forming themarine platform may float in a body of water. The buoyancy provided bythe floaters reduces the bearing pressure on the founding stratum in atemporary state or in a permanent state. By employing a unique conematching technique described hereafter in more detail, the bottom of thefloater can easily be fixed to the seafloor. As the floater interior isa relatively large space, a piled foundation for the marine platform canbe realized by installing small diameter piles through the inside of thefloater and down into bedrock, and by constructing the pile cap therein,which secures upper ends of the piles within the floater. Furthermore,these procedures may be performed in a dry working environment.

In one example, as illustrated in more detail hereafter, the partiallyfloating supported offshore marine platform may include a plurality ofbeams, each horizontally arranged and connected between adjacentfloaters so as to form the marine platform. The floater as previouslynoted is a hollow, cylindrical member capped at its upper and lower endsby slabs. The lower end may be tapered; for example, the bottom slab maybe conically-shaped (as a single cone shape or as a plurality ofcone-shapes) with the apex of the cone pointing downward toward theseabed/seafloor. The floater has a buoyancy capable of allowing thefloater itself to float, and compensates part or all of the dead weightof the marine platform when the platform is deposited in a body of water(marine environment).

The floaters and beams forming the marine platform structure areconstructed by a match casting segmental construction method, whichincludes the casting of a number of matching segments in a factory orcasting yard to assemble the floaters, beams, and deck (if any); thesegments are joined together in a harbor or dock side so as to finallyassemble the floaters and horizontal beams into a marine platform thatcan float in a body of water.

In one example embodiment, the marine platform comprises only a single,vertically aligned, hollow cylindrical floater capped at both ends byslabs, with the bottom slab having a single cone shape or multiple coneobject shapes with the apex pointing downward.

In another example, the floater may be tapered out at its lower end sothat the bearing pressure on the founding stratum can be minimized to asmall value for gravity type floaters. This tapered out floater canaccommodate raking piles (piles installed at an angle) to be installedeasily in a piled floater.

In general, a cone matching method unique to this patent application isused to fix the marine platform into the seabed. In general, and at thecorresponding location of where the floater (or floaters) of theplatform is to be secured in the seabed, the bottom cone-shaped slab ofthe floater, which points vertically down toward the seafloor, contactsand is secured to a mirror-image indentation of the cone shape of thebottom slab, or “reversed cone” that is impressed of formed into aconcrete bed within the seabed (the concrete bed having been made by amass concrete deposit in a pothole formed by removing soft materials onthe seafloor, exposing the founding layer).

In general, the above steps form part of an example construction methodfor installing the marine platform in a marine environment, to befurther illustrated in detail in accordance with the exampleembodiments. For example, the method may include, at the correspondinglocation of where the cone-shaped bottom slab of the floater is to beattached in the seafloor, excavating, dredging or sucking away softmaterial to expose a firm stratum of material in the seabed that canwithstand the expected load of the marine platform. The marine platformis then floated in position and at the same time the concrete bed isprepared by filling the pothole(s) left by the excavation in theseafloor with concrete from construction vessels using a pipe down tothe seafloor according to established underwater concreting technology.In an example, the quantity of concrete used for forming the concretebed should be such that the cone shape of the bottom slab may becompletely immersed and covered up by the concrete bed.

Prior to the concrete setting in the pothole to form the concrete bed,the marine platform is lowered down within the marine environment(water) by adjusting its buoyancy with water in-take until thecone-shaped bottom slab(s) of the floater(s) are completely immersedwithin the still-wet concrete bed. The orientation and level of themarine platform is maintained until the concrete starts to set, i.e.,starts to harden. At that point, high pressure water is used to flushseparate the two faces of the cone-shaped bottom slab(s) and theconcrete bed and the platform is thereafter raised off the concrete bed,thereby revealing the mirror-image, reversed cone indentation(s) thatwere formed in the concrete bed by the cone-shaped bottom slabs of thefloater(s).

Once the concrete of the concrete bed has reached its design strength,the platform is lowered again so that the cone-shaped bottom slab of thefloater contacts the reversed cone-shaped indentation in the concretebed. Level and orientation of the marine platform is maintain, with angap(s) formed between faces of the bottom slab and concrete bed cementgrouted via pipes pre-installed within the interior body of the floater;this completes installation of the platform in the seabed of the marineenvironment.

In another example, a pressure piping system may be installed in thefloater to deliver high pressure water jets from a high pressure watersource, and cement grout from a grout source through openings that areformed in the bottom of the floater. Pumping machinery may be locatedinside the floater, or from outside in the construction vessels.

According to another example as to be described in further detailhereafter in the example embodiments, a piling support arrangement maybe provided for the marine platform (to accommodate deeper water depths,for example). Piling may be added to the platform foundation in caseswhere the concrete founding stratum (concrete bed) for the cone-shapedbottom slab of the floater cannot resist further loads imposed on thefounding stratum.

In providing the piling support arrangement, generally a plurality ofsmall diameter piles are installed through the inside space of thefloater with their lower ends to be secured in bedrock; raking piles maybe installed if necessary, and a pile cap is then cast within the lowerend of the floater to secure the upper ends of the piles.

In additional detail, procedures for installing the small diameter pilesmay include, but are not limited to: casting a plurality of recess holeswithout steel bars in the bottom slab at the piling locations;installing each pile by one of boring/drilling/driving using establishedpiling technology, where the small piling plant (machine) may eitherrest on the floater top slab, or rest within the floater interior on topof the bottom slab once the ingress of water has been dealt with. Eachpile penetrates through a recess hole in the cone-shaped bottom slab, soas to extend down into and through the concrete bed, through thesoil/sand strata beneath the seabed, with their lower ends finallysocketed into bedrock.

Once the piles are secured in bedrock, the floater interior is dewateredby pumping, or by adding concrete at the bottom of the floater to form aconcrete plug which stops water seeping out; the interior of the floaterthus realizes a dry working environment. Then, upper ends of the pilesare cut to a desired level and made ready for a pile cap castingaccording to established procedures. For example, pile cap reinforcementbars for the pile cap are connected at their ends and fixed (by lappingsteel) to bar connectors embedded within the interior floater wall at alower end thereof. The pile cap is then cast with concrete to completeinstallation of the piling support arrangement.

In an aspect, a stiffened ring slab may be optionally joined to thebottom slab of the floater to increase the bearing surface area in orderto reduce the bearing stress in the soil stratum of the seabed. Inanother aspect, a circular, bottomless, steel can may be dropped intothe excavated pothole with a diameter that is larger than the outer mostdiameter of the floater or stiffened ring slab. Reinforcement bars maybe welded to an inner face of the steel can over the lower part of theconcrete bed for the confinement of concrete and reinforcing of theto-be-formed concrete bed. In a variant, the bottomless steel can may bereplaced by dumping stone and gravel at the perimeter of the pothole toform a rubble wall/mount that confines the concrete.

In another aspect, the bottom slab of the floater and concrete bedunderneath can be joined together by post-drilling holes through the twowith grouted steel rods to provide a shear key function. In a furtheraspect, a plurality of individual platforms may be joined to form alarge platform.

Another example as to be described in further detail hereafter in theexample embodiments is directed to a method of assembling the marineplatform at a harbor site, the platform to be used for supportingoffshore wind turbines, bridges and marine buildings in a marineenvironment. The method, in general, includes but is not limited to thefollowing steps below.

Initially, segments which are to make up the floaters and horizontalbeams are match casted in a factory or casting yard. The floatersegments are transported to the assembly harbor site and towed to aspecific assembly location at the harbor site. For the assembly, atleast three (3) guiding piles are driven into the seabed at the assemblylocation for the floater; these guiding piles are capable of supportingan overhead frame/truss for lifting the segments. The segments which areto make up the floater are then placed in the assembly location andconfined by the guiding piles, the segments are verified to be able tofloat on the water, using the guiding piles to adjust the position, andthen joined together to realize the floater. For the segment of thefloater that is to include the connection points for the horizontalbeams, an overhead frame/truss is used to hang the section of thefloater so that the connection of beams to floater can be performedabove water level. However, if this section of the floater has adequatebuoyancy, then the overhead frame/truss is not required.

A next step is to float in or bring in (such as by barge) thosehorizontal beams to be connected to the floater(s). By using temporarysupport in the guiding piles, the beams to be connected are lifted andtemporarily fixed into position on the floater(s). Any gap at the jointsor connection points between the floater and an end of a beam is thenfixed and lapped with steel bar from both ends; shutter formwork iserected, and joints at the beam/floater interfaces are cast withconcrete; this completes assembly of the marine platform. As thenow-completed marine platform is designed to be able to float on itsown, the guiding piles and overhead frame/truss are removed from theassembly location so as to free the platform, which is now free to betowed away.

The advantages of the above-described partially floating supportedoffshore marine platform for offshore wind turbines, bridges andbuilding structures include the adaptability for different water depthsand different seabed conditions. For example, and for shallow water orwhere bedrock or the founding stratum is close to the seabed level, asingle gravity-type floater can be used by using the matching cone andreverse cone technology as described above to fix the platform on theseabed. Additionally, for medium depth water, a single or multiplefloater platforms can be used with small diameter drill-in piles ordrilled in steel H-piles. The small piling machine rests on the platformtop slab to perform the piling work above sea level, in dry conditions.Therefore, large and expensive offshore piling vessels are no longerneeded. Furthermore, the risk associated with manual working under wateris now eliminated.

Example embodiments hereafter also relate to another construction methodfor installing the marine platform in a marine environment. In general,the steps in this construction method include but are not limited to thefollowing. Initially, the marine platform is floated into the marineenvironment at a desired location for installation; its co-ordinates andorientation are adjusted as needed to maintain its position and sink theplatform to the bottom of the seabed by taking in water. When it issitting firmly on the seabed, high pressure jets from the nozzles in thebottom slab are used to clear soft material until a bedrock surface orthe designed founding layer is exposed, thereby creating potholes in theseabed.

Next, and using a built-in tremie concrete down pipe provided in thefloaters, wet concrete is poured into the water-jet cleared pot holesand at the same time, the platform position and level is maintained toallow the concrete to completely cover the cone-shaped bottom slab ofthe floater, up to the level of the stiffened ring slab (if present).After the concrete becomes hardened, the platform is raised by reducingits water ballast, so that the concrete bed can be cured without theinfluence of wave and current action that would be transferred by theplatform onto the concrete bed, were the bottom slab to remain on theconcrete bed. Thereafter, the remaining procedures are similar to thosedescribed in the above construction method and are not repeated here.

General concepts of the example embodiments having been described above,the following FIGS. 1-4 should be referred to for describing an exampleembodiment directed to a partially floating, supported offshore marineplatform 10 for offshore wind turbines, bridges and marine buildings,the platform adapted for a water depth of at least five (5) meters in amarine environment, more specifically by a work example 1 below.

Work Example 1

Referring to FIGS. 1-4, the intention is to install a marine platform 10as described in the example embodiments in a marine environment of anopen sea that is 25 m deep for the support of a 3 MW horizontal axiswind turbine 5. The marine platform 10 constructed in accordance withthe example embodiments has the benefits of a hollow, cylindrical,vertically disposed buoyancy tube (“floater 1”) having a buoyancy thatcan offset up to ½ of its dead weight. The ballast of water inside thefloater 1 can change the base frequency of the structure so as to avoidthe max wind energy spectrum earthquake energy.

In the example of FIG. 1, which is a perspective view of an examplemarine platform 10 in a marine environment supporting a wind turbine 5thereon, the marine platform 10 is shown to include three (3) verticallyaligned floaters 1 connected by primary and secondary horizontal beams32, 34; these floaters 1 are supported by a partial buoyancy force. Inthis platform 10, a plurality of small diameter piles 27 are installedat the bottom of each of the floaters 1. The piles 27 are anchored attheir lower ends to the bedrock 40 (shown in later figures) or to thefounding stratum 14 (shown in later figures). Additionally, a bottomslab 2 of the floater 1 may be cast in a conic shape, with its conepointing downward toward the seabed 6 (see FIG. 4, for example).

As best shown in FIG. 2B, which is a bottom view of the cone-shapedbottom slab 2 of floater 1, and also referring to FIG. 2C whichillustrates an enlarged, front view of a lower section of floater 1, theinner face of the cone-shaped bottom slab 2 has a plurality of circularrecess holes 39 formed therein. Referring now to FIG. 4, illustrating afront view of a marine platform 10 with piling support in a marineenvironment, each pile 27 is guided down into the interior of floater 1and through these recess holes 39 (see FIG. 2C), so as to penetrate intoand through a concrete bed 9 formed in, and soil/sand strata 13 beneaththe seabed 6, with lower ends of the piles 27 thereof to be finallysocketed into the bedrock 40 or founding stratum 14.

FIG. 1 further shows three floaters 1 inter-connected with beams 32, 34to form a platform 10 with one of the floaters 1 to be installed with ahorizontal axis wind turbine 5 disposed vertically thereon. It is alsopossible to use one single floater 1 to form the platform 10, as shownhereafter in FIG. 9. As best shown by FIG. 3, which is a bottom view ofmarine platform 10 in another configuration, a single-floater platform10 may comprise a vertically disposed floater 1 and a stiffened ringslab 4 extending outward from bottom slab 2 at the bottom of the floater1, with or without the small diameter piles 27.

In a multi-floater platform as illustrated in FIG. 1, a spatialstructure is formed by connecting a plurality of vertically disposedfloaters 1 with the horizontal beams 32, 34, with or without smalldiameter piles 27 in group fixed to the bottom of the floaters 1.Although FIG. 1 shows a marine platform 10 configured in a triangularshape in plan, the example embodiments are not so limited, as marineplatform 10 may be configured in other shapes, such as square,rectangle, pentagon, etc. The cross-section of the floater 1 can also bea polygon other than a circular shape. In this work example 1, exampledimension and member sizes may be taken as: height of floater 1—30 m;floater 1 wall thickness—0.35 m; top slab 16 thickness—0.35 m to 0.5 m;cone-shaped bottom slab 2 thickness—0.35 m to 0.6 m.

In FIG. 1, marine platform 10 consists of hollow, cylindrically-shapedfloaters 1. However, the floater 1 can be of a tapered shape with itsbottom diameter greater than the top diameter to increase stability andreduce the bearing pressure on the bearing stratum. Furthermore, thestiffened ring slab 4 can be added to the bottom of the floater 1 toincrease the surface area further, in order to further reduce thebearing pressure.

As further shown in FIG. 1, the marine platform 10 may further include aregulating tower section 3 vertically disposed on top of the floater 1that supports the wind turbine 5. The height of the regulating towersection 3 should be such that a portion of the regulating tower sectionextends above the max designed wave height in the marine environment.

As best shown in FIG. 2A, which is a front view of a floater 1, theinterior of the floater 1 may be pre-installed with a pressure pipingsystem that comprises a plurality of pressure pipes 37 for pumping highpressure water (via one or more valves 38 arranged at the top of floater1 connected to a water source) or cement grout (via valves 38connectable to a cement grout source) to the bottom water side of thefloaters 1. The valves 38 control the flow of high pressure fluidsthrough pressure pipes 37. For example, pumping of high pressure waterjets or cement grout may be done by coupling the inlet (valves 38) witha water pump or concrete/cement grouting plant. The outlets of thepressure pipes 37 are at the water side of the bottom slab 2. The waterpipes 37 are used for flushing the seabed 6, and to flush open a gapthat is formed between the cone-shaped bottom slab 2 and the concretebed 9, as to be described in more detail hereafter.

Optionally, the floater 1 can be filled with water or sand to increaseits self weight in order to further stabilize the floater 1 in themarine environment. Additionally, for a 3 MW horizontal axis windturbine 5, a steel tower thereof will have a height of approximately 65m; the nacelle is placed on top of the tower and has a weight ofapproximately 400 t.

In the work example 1, which illustrates a design of a marine platform10 for wind turbine support, one issue is to resist the uplifting forcein the floater 1 induced by a huge overturning moment. In thecalculation, the small diameter piles 27 may have a diameter of about0.3 m, the portion of the piles 27 that are embedded into bedrock 40have a length of about 3 m, reinforcement bars 42 for a pile cap 17 tobe formed within the floater 1 (as described hereafter) are 3×50 mm,high pressure grouted mini-pile. A horizontal load on platform 10 isresisted by the stiffened cone-shaped bottom slab 2 which translates theforce to the concrete bed 9, which in turn translates the force into thebearing stratum 13.

Work Example 2

FIG. 12 is a perspective view which shows a bridge pier 21 comprisingbridge columns 35 and a capping beam 36 which supports bearings of thebridge pier 21. The bridge pier 21 is supported on marine platform 10which in turn is supported by two (2) floaters 1 and a plurality of thesmall diameter piles 27. In this work example, floater 1 may have adiameter of 8 m, a height of 30 m, wall thickness 0.4 m for water depth30 m, soil/sand layer 25 m, with the small diameter piles 27 to besocketed into bedrock 40.

Work Example 3

FIG. 13, which is a front perspective view of a marine platform 10 inanother configuration, shows the platform 10 in a grid formation with aplurality of floaters 1 located at respective nodes of the grid. Themain structure frame is formed by connecting main (primary) beams 32arranged horizontally between adjacent floaters 1 at upper ends thereof,and connecting optional main (secondary) beams 34 arranged horizontallybetween adjacent floaters 1 at lower ends thereof. A plurality ofadditional beams 33 branch out to suit the building layout.

In an example, a basic module for an offshore building platform mayinclude four (4) cylindrical floaters 1 supporting a grid of beams 30m×30 m overall. The size of the platform may be increased by combining anumber of the basic modules. For example, FIG. 14 is a top viewillustrating a substantially larger platform comprising a number ofinterconnected modules. In this work example, the dimensions and sizesof structural members comprising the marine platform 10 may be thefollowing: water depth—30 m; soil/sand strata 13—20 m; floater 1:diameter—8 m, height—30 m, wall thickness—0.4-0.5 m, top slab 16 andbottom slab 2 thicknesses—0.4-0.6 m.

Work Example 4

The following FIGS. 5-8B should be referred to aid in understanding aconstruction method for installing the marine platform 10 in the marineenvironment for supporting offshore wind turbines, bridges and marinebuildings. In particular, FIGS. 5-8B illustrate steps in theconstruction method for the installation of a tapered, single floaterplatform 10 on the seabed 6.

FIG. 5 is a side view to illustrate dredger operations in the marineenvironment to describe a step of excavating seabed 6 beneath thesurface 8 of the water. Specifically, FIG. 5 shows a dredging arm 22from a dredger vessel 23 on the water surface 8 extending down to theseabed 6 so as to excavate soft materials in the seabed 6 to expose thefounding stratum 14. A pothole 15 is formed in seabed 6 due to theexcavation thereof.

FIG. 6 is a side view to illustrate a step of concrete bed formingoperations in the seabed 6 of the marine environment. Specifically, FIG.6 illustrates an operation vessel 26 on the water surface 8 employing atremie concrete pipe 31 that extends between the operation vessel 26 andthe pothole 15 to pour concrete in the pothole 15 so as to form aconcrete bed 9 confined by the rubble wall/mount 7 (built up on sides ofpothole 15 in advance), and at the same time a single-floater marineplatform 10 is shown being floated in at water surface 8.

FIG. 7A is a side view of the single-floater platform 10 to illustrate astep of hovering platform 10 just above the concrete bed 9, and FIG. 7Bis a side view illustrating a step of lowering of the single-floaterplatform 10 into the concrete bed 9 so as to form the mirror-imagereversed cone indentation in concrete bed 9 with the cone-shaped bottomslab 2. In FIG. 7A, prior to the concrete being set, the platform 10 islowered so as to hover above the concrete bed 9 in the seabed 6. Asshown in FIG. 7B, the platform 10 has been further lowered so as to beat a design level, with the cone-shaped bottom slab 2 completelyimmersed within the still wet concrete bed 9.

FIG. 8A is a side view of the single-floater platform 10 to illustrate astep of raising the platform to reveal the mirror-image reversed coneindentation in concrete bed 9, and FIG. 8B is a side view of thesingle-floater platform 10 to illustrate a step of again lowering theplatform 10 so that the cone-shaped bottom slab 2 rests in themirror-image reversed cone-shaped indentation 11. The position of theplatform 10 is maintained on the concrete bed 9 until the wet concretewhich forms the concrete bed 9 is at an initial set where it begins toharden. Thus, as shown in FIG. 8A, the platform 10 is thereafter raisedonce the concrete in the concrete bed 9 has set (hardened), leaving amirror-image reversed cone-shaped indentation 11 in the concrete bed 9.In FIG. 8B, the platform 10 is lowered again to rest on the concrete bed9 with the cone-shaped bottom slab 2 fitting snugly in the mirror-imagereversed cone indentation 11 in concrete bed 9.

Any material that is present between the cone-shaped bottom slab 2 andthe reverse cone-shaped indentation 11 is then flushed out using thehigh pressure water jets through pipes 37 in the pressure piping systemto separate the two and create a gap therebetween. Once flushing iscompleted, the platform 10 is again raised, then lowered so that thecone-shaped bottom slab 2 contacts the reverse cone-shaped indentation11 with the gap therebetween. The gap present between the two faces ormeeting surfaces of the cone-shaped bottom slab 2 and reversecone-shaped indentation 11 is then subject to pressure grouting withcement grout 12. This is done using the pipes in the pressure pipingsystem so as to finally fix the marine platform 10 to the concrete bed9.

FIGS. 9-11 are provided to illustrate an optional process in theconstruction method to provide a piling support arrangement for thefixed marine platform 10. In FIG. 9, which is a side view of theplatform 10 fixed to the concrete bed 9, there is shown a small diameterpile 27 being installed with a small boring plant 24 situated within theinterior of floater 1 at the bottom thereof. This is done for each pile27. As is known, the boring plant 24 is used for installing a pile by aboring action to bore a hole in the concrete bed 9 and soil/sand strata13, with or without a casing 25 depending on the soil properties.Typically, a casing 25 will be used in the top region of the soil/sandstrata 13. Accordingly, a hole is bored through the concrete bed 9 andsoil/sand strata 13 so that the pile 27 may be extended down through arecess hole 39 in the cone-shaped bottom slab 2 to penetrate theconcrete bed 9, soil/sand strata 13 and finally to be socketed intobedrock 40. FIG. 9 also initially illustrates steel bar connectors 41 (amechanical connector) which are embedded in the interior wall of thebottom segment of the floater 1 at time of casting the bottom segment atthe factory. As will be shown hereafter, ends of a plurality of pile capreinforcement bars 42 are connected (via short steel bars 48) and fixedto these embedded bar connectors 41 prior to casting of the pile cap 17within the interior of floater 1.

FIG. 10A shows the boring plant 24 executing boring of a pile 27 using acasing 25 from the top end of the platform 10. FIG. 10B shows a pilingplant 28 driving a pile 27 downward through the casing 25 from the topof the platform 10. As is known, the piling plant 28 could be embodiedas a boring plant or percussion plant and is used to drive a pile intothe soil/sand strata 13 and bedrock 40 by force.

FIG. 11 is a side view of the platform 10 fixed to the concrete bed 9with a complete piling support arrangement. The piling supportarrangement includes a plurality of small diameter piles 27 (andoptionally raking piles 45) having been installed with their lower endssocketed in the bedrock 40, and with their upper ends having been cut tolevel and concrete at the top of the outer casings of the piles 27broken away so as to expose internal steel bars 43 at the top of thepiles 27 that are secured within a pile cap 17 that is cast into thebottom of the floater 1.

To realize the final piling support arrangement, and after the lowerends of the piles (which penetrate through the concrete bed 9, soil/sandstrata 13 between the seabed 6 and bedrock 40) have been finallysocketed into the bedrock 40, the interior of the floater 1 isdewatered. This may be accomplished either by pumping the water out, orby forming a concrete plug at the lower end therein to stop waterseepage prior to dewatering for a dry working environment. Next, theupper ends of the piles 27 (and 45) are cut to level in preparation fora known casting procedure to form a pile cap 17 within the interior ofthe floater 1 at a lower end thereof. The pile cap 17, once cast,secures the upper exposed internal steel bars 43 extending from theupper ends of the piles 27 therein.

FIG. 15 is an enlarged front view of a lower portion of the floater 1 tohelp illustrate the steps of securing the upper ends of the smalldiameter piles 27/raking piles 45 and forming the pile cap 17 tocomplete the piling support arrangement. Recall that the inner wall atthe floater 1 lower end includes the plurality of steel bar connectors41 embedded therein. Also recall that prior to casting the pile cap 17,the upper ends of the piles 27/45 are leveled and concrete in the outercasings thereof broken away to expose internal steel bars 43 at the topof the piles 27.

Further, and also prior to casting of the piling cap 17, short steelbars 48 are attached to the bar connectors 41, and a plurality ofhorizontally extending steel pile cap reinforcement bars 42 that aretransverse to the bar connectors 41 are arranged between the embeddedbar connectors 41 and connected to the bar connectors 41 via the shortbars 48. Connection points between ends of the short steel bars 48/endsof the pile cap reinforcement bars 42 and ends of the short steel bars48/bar connectors 41 are then lapped with steel, fixing them together.Thereafter, concrete to form the pile cap 17 is cast within the floater1 to complete the installation of the piling support arrangement.

Work Example 5

The casting of the concrete bed 9 on the seabed 6 optionally can beformed without employing excavation vessels as indicated above, providedthat geological conditions of the seabed 6 are favorable.

In this example, the platform 10 is equipped with a high pressure waterjet and a concrete pipe which opens to the water side in the bottom slab2. For shallow bedrock 40 in the seabed 6 with a layer of relativelythin soft material, the concrete bed 9 can be made by the platform 10itself.

Initially, the platform 10 may be floated into position at a desiredlocation within the marine environment and sunk to the bottom of theseabed 6 by taking in water. When it is sitting firmly in the seabed 6,high pressure jets from nozzles in the bottom slab 2 are used to clearsoft material, until bedrock 40 or the designed founding layer isexposed, thus forming the potholes 15 in the seabed 6. Next, a built-intremie concrete down pipe provided in the floaters 1 is used to pour thewet concrete into the water jet cleared potholes 15, and at the sametime the position and level of the platform 10 is adjusted andmaintained to allow the concrete pour to completely cover theconed-shaped bottom slab 2, and level with the stiffened ring slab 4 (ifany).

After the concrete has hardened, the platform 10 is raised by reducingits water ballast, so that the concrete bed 9 can undergo curing withoutthe influence of wave and current that the platform 10 would haveendured otherwise, if it remained in the concrete bed 9. After theconcrete bed 9 (with the mirror image, reverse cone-shaped indentation11) has cured so as to reach its design strength, the platform 10 isthen lowered again and sits on the concrete bed 9 so that theconed-shaped bottom slab 2 slides in the mirror image, reversecone-shaped indentation 11 formed in the concrete bed 9. Thereafter, byusing the pre-installed pressure piping 37 to inject cement grout 12, agap formed between the faces or meeting surfaces of coned-shaped bottomslab 2 and mirror image, reverse cone-shaped indentation 11 is filledwith the cement grout 12 so as to finally fix the floater 1 onto theseabed 6.

The present application also provides a method of assembling the marineplatform 10 at a harbor site. The method includes a step of segmentalmatch casting, in a factory or casting yard, of a plurality of firstsegments to be assembled into the hollow, cylindrical buoyancy tube(i.e., floater 1) to be disposed vertically in the marine environment.In an example, the assembled marine platform 10 may include a pluralityof floaters 1. Additionally, the method includes segmental matchcasting, in the factory or casting yard, of a plurality of secondsegments to be assembled into an elongate horizontal beam (32 and/or 34)to be connected between adjacent floaters 1. In an example, theassembled marine platform 10 may include a plurality of horizontal beams32, 34 interconnected between a plurality of sets of adjacent floaters1.

At least three guiding piles for each floater 1 are installed, at theharbor site, at the location where the floater 1 is to be assembled, tobe used as a confining mechanism for confining a first segment intoposition and supporting the weight thereof by an overhead frame/truss.

The plurality of cast first segments to assemble the floaters 1 is thentransported to the harbor site. A first segment (that is to be thebottom segment of the to-be-assembled floater 1) is lifted into positionby use of a floating crane, and guided by the guiding piles, the bottomfirst segment being floatable under its own weight and the weight of animmediate first segment placed on top of it. Of note, the bottom firstsegment is cast at the factory yard with the plurality of bar connectors41 embedded within an inner wall thereof. A next first segment is liftedand placed onto the bottom first segment, with pre-stressing being usedto join this next first segment to the bottom first segment. Theprocesses of lifting and joining are repeated for subsequent firstsegments to complete the assembling of the floater 1, each of theassembled floaters 1 including one or more joints for connection to oneor more horizontal beams 32/34.

The completed floater 1 is then hung so that it extends vertically fromthe overhead frame/truss and is restrained by the guiding piles, inpreparation for connection to the horizontal beams 32/34. Next, theplurality of second segments to make up the beams 32 and/or 34 istransported to the harbor site. These second segments are also assembledby the use of pre-stressing to join the second segments together so asto form the horizontal beam 32 and/or 34. Each completed or formedhorizontal beam 32, 34 is then sequentially lifted by a floating craneonto a temporary support on the guiding piles. Steel bars in both thefloaters 1 and completed beams 32, 34 are then fixed together andthereafter lapped with steel.

All the joints where ends of horizontal beams 32, 34 meet a floater 1are then cast with in-situ concrete until all beams 32 and/or 34 arefixed to the floaters 1. The overhead frame/truss and guiding piles arethen removed from the assembly location at the harbor site, with thecompleted marine platform 10 configured to be floated out into themarine environment. Optionally, a wind turbine 5 may be installed on topof one of the floaters 1 of marine platform 10.

As previously described above, the bottom slab 2 may beconically-shaped, either as a single cone shape or as a plurality ofcone-shapes, with the apex of the cone pointing downward toward theseabed/seafloor. FIG. 16 is a side perspective view of a single-floatermarine platform 10 in which the bottom slab 2 has a plurality of coneshapes 46 on an underside thereof. As part of the above-described methodof installing the platform 10 in the marine environment, these coneshapes 46 become immersed in the still wet concrete within concrete bed9 so as to form a plurality of mirror-image reversed multi-cone-shapedindentations 47, as shown in FIG. 16.

The example embodiments hereinabove having been described, it will beapparent to those skilled in the relevant art that some features thatare not particularly important to an understanding of the partiallyfloating supported marine offshore platform 10 may not be shown for thesake of clarity.

Further, it should be understood that the partially floating supportedoffshore platform 10 for offshore wind turbines, bridges and buildingsdisclosed herein is not limited to the specific example embodimentsdescribed above. Various changes and modifications thereof may beeffected by one skilled in the art without departing from the spirit orscope of protection. For example, elements and/or features of differentillustrative embodiments may be combined with each other and/orsubstituted for each other within the scope of this disclosure.

1-19. (canceled)
 20. A partially floating, supported offshore marineplatform for offshore wind turbines, bridges and marine buildings, theplatform adapted for a water depth greater than 5 meters in a marineenvironment, comprising: at least one hollow, cylindrical buoyancy tubehaving a tapered lower end and disposed vertically in the marineenvironment, wherein the tapered lower end is embodied as aconically-shaped bottom slab with the apex of the cone-shaped bottomslab pointing downward towards a seabed, and the cone-shaped bottom slabof the at least one buoyancy tube is fixed to a concrete bed that hasbeen cast on the seabed so as to support one of a wind turbine, bridge,and marine building on the marine platform in the marine environment.21. The marine platform of claim 20, further comprising: a plurality ofelongate piles having upper ends attached to the cone-shaped bottom slaband extending toward the seabed with lower ends thereof affixed tobedrock below the seabed, the piles with the cone-shaped bottom slabproviding a counter force to counterbalance an uplifting force of the atleast one buoyancy tube.
 22. The marine platform of claim 20, theplatform further comprising a plurality of buoyancy tubes interconnectedby a plurality of horizontal beans so as to form a triangular-shapedmarine platform, wherein one of the buoyancy tubes supports a windturbine disposed vertically thereon.
 23. The marine platform of claim20, further comprising: a stiffened ring slab extending outward from theconed-shaped bottom slab at the lower end of the buoyancy tube toincrease surface area so as to further reduce bearing pressure.
 24. Themarine platform of claim 20, further comprising: a vertically-disposedregulating tower section affixed to the at least one buoyancy tube at anupper end thereof and supporting a wind turbine thereon, a height of theregulating tower section configured so as that at least a portion of theregulating tower section extends above a determined maximum wave heightin the marine environment.
 25. The marine platform of claim 20, furthercomprising: a pressure piping system installed within the hollowinterior of the at least one buoyancy tube, and one or more valvesprovided at an upper end of the at least one buoyancy tube, the valvesconnected to the pressure piping system and connectable to a source ofhigh pressure water for pumping a high pressure water jet through thepressure piping system to remove soft material on the seabed, to flushopen a gap formed between a face of the coned-shaped bottom slab and asurface of the concrete bed, and to pressure grout the gap between theconed-shaped bottom slab and concrete bed.
 26. The marine platform ofclaim 20, wherein the at least one buoyancy tube is filled with one ofsand and water to increase self-weight of the marine platform so as tocounter an uplifting force induced by wind loads on the platform.
 27. Aconstruction method for installing the marine platform according toclaim 1 in the marine environment for supporting offshore wind turbines,bridges and marine buildings, comprising: excavating soft materials atthe seabed at a location where the at least one buoyancy tube of theplatform is to be erected by one of a dredging, sucking, and flushingmethod so as to form a pothole in the seabed, pouring wet concrete forforming the concrete bed into the pothole by using one of a gravity orconcrete pumping method, lowering the platform until the cone-shapedbottom slab of the at least one buoyancy tube is immersed within theconcrete bed prior to an initial setting of the wet concrete which formsthe concrete bed, the cone-shaped bottom slab forming a mirror image,reverse cone-shaped indentation in the wet concrete of the concrete bed,maintaining position of the platform until the wet concrete which formsthe concrete bed is at an initial set where it begins to harden,flushing out material between the cone-shaped bottom slab and thereverse cone-shaped indentation formed in the concrete bed to separatethe two and create a gap therebetween, raising the platform uponcompletion of the flushing step, lowering the platform a second time sothat the cone-shaped bottom slab contacts the reverse cone-shapedindentation formed in the concrete bed within the seabed with the gaptherebetween, and pressure grouting the gap between meeting surfaces ofthe cone-shaped bottom slab of the at least one buoyancy tube andreverse cone-shaped indentation formed in the concrete bed so as tofinally fix the marine platform to the concrete bed.
 28. A constructionmethod for installing the marine platform according to claim 1 in themarine environment for supporting offshore wind turbines, bridges andmarine buildings, the marine platform further including a pressurepiping system installed within the hollow interior of the at least onebuoyancy tube, and one or more valves provided at an upper end of the atleast one buoyancy tube which are connected to the pressure pipingsystem, connectable to a source of high pressure water for pumping highpressure water jets through the pressure piping system, and connectableto a cement grout source for pumping cement grout through the pressurepiping system, the construction method comprising: floating the marineplatform into position within the marine environment such that the atleast one buoyancy tube of the platform hovers at a desired locationabove soft material in the seabed, flushing the soft material away atthe desired location using the high pressure water jets through pipes inthe pressure piping system until a founding layer is reached, therebyforming a pothole which exposes the founding layer in the seabed,lowering the marine platform further within the marine environment sothat it is directly over the pothole formed in the seabed, pouring wetconcrete for forming the concrete bed into the pothole using one of agravity or concrete pumping method, continue lowering the platform untilthe cone-shaped bottom slab of the at least one buoyancy tube isimmersed within the concrete bed prior to an initial setting of the wetconcrete which forms the concrete bed, the cone-shaped bottom slabforming a mirror image, reverse cone-shaped indentation in the wetconcrete of the concrete bed, maintaining position of the platform untilthe wet concrete which forms the concrete bed is at an initial set whereit begins to harden, flushing out material between the cone-shapedbottom slab and the reverse cone-shaped indentation formed in theconcrete bed using the high pressure water jets through pipes in thepressure piping system to separate the two and create a gaptherebetween, raising the platform upon completion of the flushing outstep, lowering the platform again so that the cone-shaped bottom slabcontacts the reverse cone-shaped indentation formed in the concrete bedwithin the seabed with the gap therebetween, and pressure grouting thegap between meeting surfaces of the cone-shaped bottom slab of the atleast one buoyancy tube and reverse cone-shaped indentation formed inthe concrete bed using pipes in the pressure piping system so as tofinally fix the marine platform to the concrete bed.
 29. Theconstruction method according to claim 27 or 28, further comprising:providing a piling support arrangement extending vertically between theat least one buoyancy tube and bedrock beneath the seabed, with endsthereof fixed within the buoyancy tube and bedrock, the providing stepfurther including: installing a plurality of individual, elongate pilesusing known boring and driving piling technology down through theinterior of the at least one buoyancy tube and through a plurality ofrecessed holes formed in the cone-shaped bottom slab so that lower endsof the piles penetrate through the concrete bed on the seabed, soil/sandstrata between the seabed and bedrock, to be finally socketed into thebedrock, dewatering the interior of the at least one buoyancy tube bypumping, or by forming a concrete plug at the lower end therein to stopwater seepage prior to dewatering for a dry working environment, cuttingupper ends of the piles to level in preparation for a known castingprocedure to form a pile cap within the interior of the at least onebuoyancy tube at a lower end thereof for securing the upper ends of thepiles therein, an inner wall at buoyancy tube lower end having aplurality of bar connectors embedded therein, arranging a plurality ofhorizontally extending reinforcement bars for the pile cap between theembedded bar connectors in the inner wall and lapping steel bar atconnection points between ends of the reinforcement bars and barconnectors, and casting the pile cap within the buoyancy tube tocomplete installation of the piling support arrangement.
 30. Theconstruction method according to claim 27 or 28, wherein, after the atleast one buoyancy tube of the marine platform is fixed to the concretebed, the construction method further comprises: ballasting the at leastone buoyancy tube by filling the hollow interior thereof with water orsand.
 31. The construction method according to claim 27 or 28, wherein,after forming of the pothole in the seabed, the construction methodfurther comprises: forming a rubble wall by dumping stones around thepothole to contain the concrete poured for forming the concrete bed. 32.A method of assembling a marine platform at a harbor site, the platformto be used for supporting offshore wind turbines, bridges and marinebuildings in a marine environment, comprising: segmental match casting,in a factory or casting yard, a plurality of first segments to beassembled into a hollow, cylindrical buoyancy tube to be disposedvertically in the marine environment, the assembled marine platform toinclude a plurality of buoyancy tubes, segmental match casting, in thefactory or casting yard, a plurality of second segments to be assembledinto an elongate horizontal beam to connected between adjacent buoyancytubes, the assembled marine platform to include a plurality ofhorizontal beams, installing, at the harbor site, at least three guidingpiles for each buoyancy tube at the location of where the buoyancy tubeis to be assembled, to be used as a confining mechanism for confining afirst segment into position and supporting the weight thereof by anoverhead frame/truss, transporting the plurality of first segments tothe harbor site, lifting, by use of a floating crane, a first segmentthat is to be the bottom segment of the to-be-assembled buoyancy tubeinto position, guided by the guiding piles, the bottom first segmentbeing floatable under its own weight and the weight of an immediatefirst segment placed on top of it, lifting a next first segment onto thebottom first segment and using pre-stressing to join this next firstsegment to the bottom first segment, repeating the processes of liftingand joining for subsequent first segments to complete the assembling ofthe buoyancy tube, each of the assembled buoyancy tubes including one ormore joints for connection to one or more horizontal beams, hanging acompleted buoyancy tube so that it extends vertically from the overheadframe/truss and is restrained by the guiding piles, transporting theplurality of second segments to the harbor site, assembling the secondsegments by the use of pre-stressing to join the second segmentstogether so as to form the horizontal beam, lifting, by use of afloating crane, each formed horizontal beam onto a temporary support onthe guiding piles, fixing steel bars in the buoyancy tubes andhorizontal beams and thereafter lapping the steel bars, casting thejoints where ends of horizontal beams meet a buoyancy tube with in-situconcrete until all beams are fixed to the buoyancy tubes, removing theoverhead frame/truss and guiding piles, floating out the assembledmarine platform into the marine environment, and optionally installing awind turbine on top of one of the buoyancy tubes of the platform.